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APOLLO 14 AS 14-70-9671.jpgAS 14-70-9671 - The "Bright One"54 visiteThis crater on the Lunar Far-Side is similar in age and size to the near- side crater Euler. It is located midway between the craters Becvar and Langemak. About 36 Km in diameter, it was informally called the "Bright One" by the Apollo 14 Astronauts because of its bright ejecta and ray pattern. The bright halo that surrounds the crater is about 150 Km in diameter. Its brightness is not evident in this view because the picture was taken when the Sun angle was low. The radial pattern of dunelike ejecta around the crater is most apparent where the Sun's rays are perpendicular to the direction of ejecta flow, as in the lower part of the picture. The hummocky or bumpy floor of the crater is caused largely by material that has slumped from the walls. Stuart A. Roosa, the Apollo 14 CMP, used a handheld camera with an 80-mm lens for this photograph. Later, using a 500-mm lens, he photographed in much more detail that part of the floor of the crater outlined in this photograph and shown in AS 14-9975.
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APOLLO 14 AS 14-72-9975.jpgAS 14-72-9975 - The "Bright One" (detail mgnf)54 visiteWhen photographed with the 500-mm lens, the abundance of blocks (bright spots with shadows extending to the right) attests to the freshness of the materials on the floor of the "Bright One". Material that has flowed and in some instances formed smooth-surfaced "pools" is evident in much of the area. Arrows mark the edge of a major flow distinguished by its surface texture, color (in the original negative), location in a topographic low, and clearly defined border. Note that the abundance of boulders in the flow is much less than in nearby areas, presumably because the flow has buried most of the boulders in its path. Scientists generally agree that material has flowed here, and on the floors and flanks of many other craters, but the nature of the material that has flowed is a matter of debate.
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APOLLO 15 AS 15-0018.jpgAS 15-0018 - On the rim of Gibbs Crater53 visiteImpact craters with asymmetric ray patterns and profiles can be caused by conditions other than the angle of trajectory. This 5-Km crater was formed when a meteoroid impacted on the North-East rim crest of Gibbs, a very much larger and older crater near the Moon's East limb. In this restricted view, Gibbs' rim is the dark area in the North half of the picture, and its wall is the light area in the south half. The rim crest extends from arrow to arrow. Discrete rays of both light and dark ejecta are well developed around the North half of the small crater where they were deposited on a relatively level surface. They are poorly developed around the South side of the small crater, probably having been partly destroyed by mixing as the ejected materials cascaded down the much steeper wall of the Crater Gibbs. Subsequent erosion has further destroyed the original pattern. The configuration of the small crater's rim has also been affected by topography.
It is sharply defined along the North side but is barely discernible along the south side where large volumes of material have slumped down the wall of the older crater.
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APOLLO 15 AS 15-0274.jpgAS 15-0274 - Euler Crater55 visiteIn this oblique view of Euler, some details are shown that are not visible in other pictures. Note, for example, the ledges (L) of bedrock cropping out along the South Wall and the low terraces (T) at the points of contact between the slump masses and the floor. They may be aprons of debris or "bathtub rings" of lava. This oblique viewing angle also enhances the polygonal outline of Euler's rim crest and the size and ruggedness of the huge masses that have slumped from the walls.
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APOLLO 15 AS 15-0757.jpgAS 15-0757 - Tsiolkovsky63 visiteTsiolkovsky is one of the most prominent features on the Far-Side of the Moon. It is a 1 90-Km- wide impact crater with a large, complex central peak that is offset from the apparent center of the crater. Differences in tone and texture between the central peak, the lava-flooded floor, the terraced walls and the ejecta blanket are dramatically displayed in this oblique view. The ejecta blanket is dominated by a coarse pattern of ridges radiating outward from the crater; superposed on this pattern are many small level pools of smooth material that are much lighter than the otherwise similar smooth dark mare in the floor of Tsiolkovsky. The pools probably originated differently. They may consist of rock that was melted by the heat and pressure generated during the impact event and that flowed into depressions before it hardened.
Cratering experiments on Earth have shown that central peaks consist of bedrock that has been displaced upward by a distance equal to about 1/10th the diameter of the resulting crater. If samples could be obtained from the central peak at Tsiolkovsky, they might be rocks that were 20 km below the Moon's surface before Tsiolkovsky was created.
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APOLLO 15 AS 15-1030.jpgAS 15-1030 - Tsiolkovsky60 visiteThis vertical view shows the central part of Tsiolkovsky in more detail. From the nature of the boundary between the dark mare lavas and the lighter materials at the base of the walls and in the central peak, we know that the lavas must have lapped upon and embayed the lighter materials. The relatively level areas of lighter material in the southwest and northwest parts of the floor have a distinctly different texture than the coarse blocky materials of slumped wall that surround the floor elsewhere. Finely cracked, furrowed, and hummocky, they closely resemble parts of the floor of the crater King. They probably consist of impact melt that solidified to form the original floor of Tsiolkovsky before it was flooded by mare lavas.
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APOLLO 15 AS 15-1541.jpgAS 15-1541 - Archimedes and Aristillus55 visiteThe ejecta blanket and secondary impact craters of the mare-filled crater Archimedes (80 Km in diameter) are visible on the terrain toward the viewer (South) but not on the mare surface to the crater's left and right. Yet at one time ejecta like that to the south must have completely surrounded Archimedes because similar ejecta surrounds craters such as Aristillus (upper right). Thus, the mare lavas, in addition to filling the interior of Archimedes, obviously have covered the eastern and western parts of the ejecta. In turn, ejecta from Archimedes has covered materials of the Imbrium Basin like the rugged hills in the lower left of the picture. These stratigraphic relations prove that time elapsed between formation of the Imbrium basin and its filling by mare-time enough for impacts to create Archimedes, the deeply flooded crater to its right (arrow), and similar "Imbrian-age" craters elsewhere, as was pointed out by Eugene Shoemaker in 1962.
Archimedes has no visible central peak complex. Presumably the complex exists but has been completely inundated by the mare.
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APOLLO 15 AS 15-2405.jpgAS 15-2405 - Craters Messier and Messier "A"55 visiteMessier (1) and Messier A (2) are a pair of unusual craters in North-Western Mare Fecunditatis. Messier is elliptical and has bright walls and light rays of ejecta extending at right angles to its long axis (approx. 16,5 Km). Messier A is a doublet crater having two very long rays or filaments of ejecta extending Westward from it. The east part of the doublet has steep, bright walls, whereas the west part is dark and appears mantled. Differences between the two parts are more clearly shown in this oblique view of Messier A (see AS 16-4471). Both craters resemble some small experimental impact craters produced in sand by projectiles following shallow trajectories (4° or less from the horizontal) at velocities of approximately 1,7 Km/s. In separate experiments using single projectiles, both elliptical craters with lateral ejecta lobes and doublet craters have been produced. Thus, it can be inferred that these lunar craters were produced by high velocity projectiles following shallow trajectories. By further analogy with the experiments, the projectiles that formed Messier and Messier A apparently traveled from east to west".
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APOLLO 15 AS 15-2510.jpgAS 15-2510 - Humboldt Crater55 visiteThe crater Humboldt, on the east limb of the Moon, as seen from Earth, is 200 km across, a little larger than Tsiolkovsky. This view by the Apollo 15 mapping camera looks southward across Humboldt's ejecta blanket and into the crater. Irregular secondary craters partly covered by the ejecta are in the foreground and a long chain of secondaries extends from Humboldt's rim to the foreground. Humboldt is one of the largest craters known to have a prominent central peak. If the crater is like terrestrial impact structures, the peak may expose rock uplifted about 10% of the crater's width, on the order of 20 Km from beneath the crater floor. This would be an exciting find for future Astronauts. A spider web of cracks on the crater floor suggested to R. B. Baldwin (1968) that the floor was bowed up in the middle. Later, dark mare lavas flooded low areas in the outer part of the floor and covered the cracks. A peculiar "bull's eye" double crater on the crater floor has several counterparts elsewhere on the Moon. The origin of these double craters is a continuing puzzle.
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APOLLO 15 AS 15-9254.jpgAS 15-9524 - Bright and Big "Streaks"54 visiteThis elliptical crater is 1 Km long with an unusual, winglike pattern of rays.
This ejecta pattern is similar to those around some small experimental impact craters produced by missiles traveling along low-angle trajectories at White Sands Missile Range, N. Mex.
From the shape of the crater and the distribution of the rays, it is difficult to tell whether the meteoroid was traveling from North to South or South to North.
The higher albedo (brightness) of the North wall and the concentration of high albedo ejecta on the North-West and North-East flanks suggest that it traveled from South to North.
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APOLLO 15 AS 15-9287.jpgAS 15-9287 - A "Middle-aged" Crater54 visiteRemarkable detail is shown in this enlargement of a small part of a panoramic camera frame. In most respects, the crater itself is typical of a great many craters its size-about 1,2 Km. Because it does not have rays, it is believed to be older than most other Lunar craters. Its rounded rim crest and slightly raised rim (extending outward to the arrow, on the West side) also point to its greater age. On the other hand, it is young enough that some of the original dunelike texture of the ejecta blanket is preserved (especially to the West), a great many large blocks of ejecta are still visible, and the original depth of the crater has not been greatly lessened by infalling debris. The largest blocks, which are about 30 mt in size, occur near the rim. The terrace (T) extending partly around the wall about 100 mt below the surface probably marks the top of a resistant rock layer. However, if there were other signs of bedrock stratification within this crater, they have been obscured by the movement of debris down the walls. The very smooth floor is the only unusual feature of this crater. It may consist of a solidified pool of rock melted by heat generated from the impact.
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APOLLO 15 AS 15-9299.jpgAS 15-9299 - Le Monnier Crater54 visiteOn January 16, 1973, the Soviet unmanned roving vehicle Lunokhod 2 was landed by Luna 21 in or near this area in the South-Eastern part of the crater Le Monnier. This crater is a large (61 Km) pre-Imbrian crater cut into terra at the Eastern edge of Mare Serenitatis before Serenitatis was flooded by mare laves. Part of Le Monnier's Southern wall fills the lower part of the picture. A conspicuous chain of elongate depressions has formed in the lava-filled floor of the crater. The chain trends 22 Km northward and its pattern is quite surely controlled by an underlying fracture system. Regionally, the inferred fracture system is concentric to the grossly circular Serenitatis Basin and in this area trends Northward. No comparably young structural features having the same trend cut the terrae surrounding Le Monnier. However, older structures having this trend occur in the southern and northern walls and rims of Le Monnier. The aligned depressions on the mare are mostly 300 to 400 mt wide and 30 to 60 mt deep. The three deepest stretches are 1 to 2 km long and about 50 to 65 m deep. These depressions probably were the locus of fissure eruptions of mare basalt. Withdrawal of the last lava back into the fissure may have created subsurface voids into which collapse took place, causing the depressions and accounting for the absence of raised rims on the depressions.
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